1. Field of Invention
The present invention relates to dental implants and more particularly, relates to a method and apparatus for more accurately fitting the primary support bar and the gold or metal copings secured thereto to the implant fixtures which have been surgically imbedded in the alveolar bone.
2. Description of the Prior Art
In the area of dental prosthetics, there have been primarily two major types of dental implant prosthetics which have been in use. The first, commonly known as the over denture, provides for support structure to be implanted into the alveolar bone which support structure extends above the gum line and permits the patient to snap fit the denture in place. This type of construction permits the patient to remove the denture himself and clean the denture and the gum area. The draw back of the over denture is that it does not normally provide sufficient stability under all eating or chewing conditions.
The second type of prosthesis in wide use is that of the fixed prosthesis. Again a support structure is anchored in the alveolar bone, the support structure extending above the gum line and the prosthesis being permanently secured to the support structure embedded in the bone. This type of prosthesis normally provides a more stable prosthesis for the patient, but aesthetic and hygiene problems arise in that the prosthesis can only be removed by a dentist to permit cleaning of the area under the prosthesis and approximate to the support structure.
U.S. Pat. No. 4,767,328 to Branemark discloses a device for providing such a permanent fixed prosthesis. Further, U.S. Pat. No. 3,748,739 to Thibert, U.S. Pat. No. 4,741,698 to Andrews, U.S. Pat. No. 3,641,671 to Roberts, U.S. Pat. No. 4,085,506 to Lew, and U.S. Pat. No. 3,514,858 to Silverman all disclose versions of permanent or fixed implants. U.S. Pat. No. 4,062,119 to Linkow discloses an implant system for use with removable over dentures.
Applicant has previously developed a dental implant prosthesis which provides for long term stability to the patient, together with the aesthetic appearances required by a dental prosthetic, yet which will permit the patient to remove the prosthesis for cleaning not only the prosthesis, but the gum area surrounding support structures in order to prevent any hygiene problems. This fixed removable dental implant system may be understood with reference to U.S. Pat. No. 4,931,016 and U.S. Pat. No. 5,057,017 to Sillard.
Applicant has continued to refine and develop the methodology utilized in fabricating the fixed removable dental implant system. The methodology relies upon electro discharge machining (EDM) for fabricating the various elements of the dental implant prosthesis as set forth in the aforesaid patents to Sillard.
A persistent problem has been the ability to match the support structure to the implant fixtures which have been embedded in the alveolar bone.
The normal procedure requires the dentist to take an impression of the patient's mouth and this is converted into a master model or actual stone cast of the patient's gum and teeth. After the surgical procedures for embedding or inserting the implant fixtures into the alveolar bone, a similar impression of the patient's gums with the embedded implant fixtures in place is taken and converted into a stone model identifying the location, height, etc., of the implant fixtures. The dental laboratory then replaces portions of the block with actual implant fixtures positioned to the exact height, angle or the like as the implant fixtures which are positioned in the patient's mouth. This fixture which is positioned in the stone model is normally referred to in the industry as the analog or replica in that it is deemed to be an exact replica of the actual implant fixture in the patient's mouth, embedded in the alveolar bone and extending above the gum line. Depending upon whether the dental prosthetic is a complete prosthetic, partial prosthetic, or single tooth prosthetic, there may be one or more implant fixtures positioned within the patient's mouth and hence one or more analogs or replicas positioned in the stone model.
In a full dental prosthetic the support bar which is generally U-shaped in configuration, is designed with a plurality of openings corresponding to the number of implant fixtures embedded in the patient's jaw and the number of analogs or replicas embedded in the stone model. The dental laboratories job is to insure that the support bar makes an accurate fit at each analog or replica location so that when it is fitted into the patient's mouth, there will be an accurate fit with each implant fixture such that when a fastener in the form of a screw is attached through the support bar and into a threaded receptacle in the implant fixture, the support bar will have no wobble within the patient's mouth.
This fitting and fabrication of the support bar in the dental laboratory involves the EDM process between the support bar and the analogs or replicas in the stone model. The exact problem in fabricating the fitting has been that in the EDM process you may be attempting to correct for a very very slight wobble by eroding a small portion of the support bar, but the EDM process may remove or erode material from the analog or replica requiring the dental laboratory technician to repeat the process with respect to all of the analogs or replicas in the stone model in order to obtain the fit desired. In actuality, the actual erosion occurs on the circumferential area on the underside of the support bar surrounding the throughbore for the fastening means. This area is referred to as a gold or metal coping in that it is a gold or metal coping having been secured to the underside of the support bar or fixed bridge or any implant restoration by suitable means (i.e. solder, casting, cement).
Applicant has solved this problem by developing a bushing for positioning between the support bar and the analog or replica during the EDM process which insures that the analog or replica will not be subject to any erosion during the EDM process when making the fitting fabrication between the analog or replica and the support structure. In this manner, the dental technician ensures that the analog or replica in the stone model remains identical to the implant fixture in the patient's mouth. Any excess erosion during the fitting and fabricating process will occur at the bushing and not the analog or replica.
The benefit of this method and the design of the bushing is that it ensures that the support structure fabricated in the laboratory with analogs or replicas will fit in the same manner once it is transferred to the patient's mouth, since the analog or replica and the implant fixture in the patient's mouth will have remained identical during the fabrication process. It can be seen that, if the support bar, in fabricating it to the analogs or replicas in the laboratory differed significantly from its implant fixture counterpart in the patient's mouth, that there could not be an accurate, secure fitting of the support bar in the patient's mouth and further, the patient, after having experienced the surgery once, most surely would not want to have to experience a second oral surgery to implant a new implant fixture.